Hard shell liquid seal earmuff with isolated inner close coupling ear shell



June 1961 M. TOUGER ETAL 2,989,598

HARD SHELL LIQUID SEAL EARMUFF WITH ISOLATED INNER CLOSE COUPLING EARSHELL Filed Feb. 24, 1960 INVENTORS MARTIN L. TOUGER ROBERT E. UL ICH BYUL! ATTORNEYS United States Patent 2,989,598 HARD SHELL LIQUID SEALEARMUFF WITH ISO- LATED INNER CLOSE COUPLING EAR SHELL Martin L. Touger,Woodbury, and Robert E. Ulrich,

River-ton, N.J., assignors to the United States of America asrepresented by the Secretary of the Air Force Filed Feb. 24, 1960, Ser.No. 10,821

6 Claims. (Cl. 179-182) This invention relates generally to acousticalcoupling :devices and, more particularly, to an acoustical couplingdevice used in connection with instruments for receiving signals fromelectro-acoustical transmitting devices.

One of the more serious problems facing manufacturers :and designers ofacoustical coupling devices, such as ear-, phone headsets for telephonereceivers or the like, is to design the unit in such a manner that thereceiving efl'lciency of the telephone receiver is not greatly impairedby externally caused noise. A particular need for such a design is foundin the aircraft industry, where it is necessary for ground maintenancecrews to have some means of intercommunication while they are workingaround modern, high performance aircraft, such as jet aircraft. Theintense noise generated by jet engines renders earphone headsets of theprior art practically useless, as the sound waves of this noise set upvibrative forces in the construction of former earphones and, due to theutilized construction of former earphones, these forces were transmittedfrom one member to another until the entire carphone was vibrating.

Theetfects of this were twofold: one, external noises were permitted toleak under the earcushion to reach the ear of the user; two, thevibrations of the earphone caused the entire headset to jump around onthe head of the user, making it not only difiicult for him to hear thesignals that were being transmitted to him through the receiver, butmaking it very uncomfortable for him to wear the headset due to itsbouncing around on his head.

There are two Ways of reducing the effects of such vibrative forces, thefirst being to provide an acoustical or a mechanical filter, such asthose used in an air-conditioning system, and the second to isolate thebody or unit from the vibrations.

Since it is desired to produce an earphone that is not only acousticallyefficient, but also light in weight, especially when it is to be worn bymen actively engaged in sometimes confined places, it becomes tooimpractical to .1188 acoustical or mechanical filters as they add to theWeight and bulk of the earphone. Therefore, the principle of isolatingthe receiver unit from the remainder of the earphone will provide alighter, less bulky and more eflicient receiving unit.

It' is, therefore, an object of the present invention to provide anearcushion providing improved sound attenuation with a minimum ofearcushion weight.

It is a further object of the present invention to provide an earcushionof a novel construction providing increased sound attenuation andallowing close coupling of earphone to the users ear.

It is another object of the present invention to provide an earcushionconsisting of an outer casing and an inner shell having a minimum volumecomprised to balance comfort against improved acoustical coupling of earto receiver diaphragm.

A still further object of the present invention is to provide anearcushion for an electrical headset consisting of an outer casing andan inner shell arranged for out-ofphase oscillatory motion relative toeach other to'damp the effects of vibrative forces impinging externallyupon the outer casing.

It is yet another object of the present invention to present anearcushion for an earphone headset comprising an 2,989,598 Patented June20, 1961 outer casing and an inner shell arranged for relative, opposingoscillatory movement, and resilient means positioned between the casingand the shell to limit the movement of the shell so that the volume ofthe acoustical cavity defined by a surface of the shell remainsminimized and substantially constant to allow close coupling of thereceiver diaphragm to the users ear.

The novel features characteristic of the present invention, as well asadditional objects and advantages thereof, will be better understood inthe following detailed description of a single embodiment thereof, whenread in connection with the accompanying drawing in which:

FIG. 1 is a side view, in section, of an earcushion in accordance withthe present invention.

Referring more particularly to FIG. 1, there is shown by way ofillustration an earcushion unit indicated generally at 1, consisting ofa hollow, annular outer casing 2, having an annular peripheral rim 16.Outer casing is constructed of a light, rigid material, such as plastic,and is similar to the standard ear protector shell currently in use.

An annular, rigid flange 12 is securely attached to rim 16, as bycementing or gluing, and is further mounted on a circumaural, annularear pad 6, being removably secured thereto by flange retaining flap 14.Ear pad 6 is a fluid filled bag of a pliable material, such as plastic,to allow it to conform to the configuration of the head of the user,thereby providing increased comfort in addition to improved sealingmeans against external noise. Integral with shell 6 is a flangeretaining flap 14 which has the function of holding flange 12 onto earpad 6.

Flange 12 is slightly inclined relative to ear pad 6 and is contoured soas to conform to the configuration of the head of the average wearer.Therefore, a downward movement by flange 12 against ear pad 6 acts onthe outer portion of ear pad 6, thereby effecting an improved sealingmeans against external noise.

An inner shell 3 is mounted on ear pad 6 independently of outer casing 2and is inclosed completely within outer casing 2. Inner shell 3 has anupper surface which is contoured to define a retaining ring 17 for soundtranslating apparatus, such as a sound powered telephone receiver. Alower surface of shell 3 defines an acoustical chamber or cavity 8 whichis shaped and contoured to accommodate the ear of the user, whereby thelower surface of shell 3 is pressed into contact with the peripheralmargins of the ear. Shell 3 actually contacts ear pad 6 by means of anannular, peripheral rim 9. Sound openings 7 are provided in shell 3 toallow sound signals to be transmitted from a receiver 4 to the usersear.

Shell 3 is positioned laterally Within casing 2 by means of resilientpositioning pads 10, which are composed of foam or sponge rubber, andare fixed against vertical slipping by securing indentations 15. It willbe understood that, while the specific embodiment of the presentinvention employs a series of such foam pads in spaced intervalscircumferentially of shell 3, a continuous ring or cup of similarmaterial may be used without departing fromthe spirit of our invention.In like manner, the securing indentations 15 may take the form of acircumferential groove.

Positioned between the top of receiver 4 and the inner surface of outercasing 2 is buifer pad 5, also composed of foam or sponge rubber. Thus,it will be seen that inner shell 3 is resiliently isolated with respectto outer casing 2.

In operation, when the earcushion 1 is worn as part of an earphoneheadset by a ground crewman, for example, and is subjected to intensenoise, such as from a jet aircraft engine, certain vibrative forces willimpinge upon the outer surface of easing 2. These forces will betransferred to flange 12 and, in turn, to ear pad 6. Since flange 12presses against the outer portion of ear pad 6, this outer portion willbe compressed against the head of the user, thereby forcing that volumeof the fluid filling 18 originally contained in the outer portion of earpad 6 into the inner portion thereof. Since the fluid filling, generallya liquid, is noncompressible, the hydraulic forces thus set up will betransferred to the rim 9 of inner shell 3, thereby imparting a motionopposite in direction and undiminished in magnitude to shell 3 withrespect to casing 2.

As shell 3 starts to move upwardly, buffer pad 5,

having been compressed by the downward movement of casing 2, offersresistance to the upward movement of shell 3 and the position of shell 3remains substantially unchanged.

, Inasmuch as the forces against outer casing 2 are vibratory in nature,they will cause casing 2 and shell 3 to oscillate in opening and closingrelation; however, due to the elastic isolation of shell 3, casing 2only will continue to have motion, since the motion of shell 3 is dampedto the point of complete cancellation.

In order to provide close coupling of receiver diaphragm to ear, it isnecessary that the acoustical cavity 8 remains substantially constant.Since the motion of shell 3 is cancelled, cavity 8 will have a constantvolume, thereby allowing close coupling between the diaphragm ofreceiver 4 and the ear of the user. This will provide for increasedsignal transmitting efficiency of receiver 4. In addition, the impedanceof outer casing 2 and the resilient reactance of the air spaces betweenouter casing 2 and inner shell 3 offers acoustical insulation againstthe penetration of external noise to interfere with receiver '4. Thesealing action of ear pad 6, due to the downwardly and inwardly movementof flange 12 responsive to vibrative forces against casing 2, preventsexternal noise from leaking under ear pad 6 to the ear of the user.

While there is illustrated and described herein but a single embodimentof the present invention, it will be apparent to those persons skilledin the art that other modifications and changes are possible withoutdeparting from the spirit of the present invention. For example, a foamfilled ear pad 6 may be substituted for a fluid filled ear pad, or afluid of lesser or greater viscosity may be used for a particularapplication. In addition, employment of a plurality of fluid or foamfilled ear pads connected by an orifice rather than a single ear pad maybe employed without departing from the spirit of the present invention.Therefore, it is desired that the particular form of the inventiondescribed herein be considered illustrative only and not as limiting.

We claim:

1. An ear cushion for an earphone headset comprising an annular, pliableear pad, a rigid annular flange mounted on said ear pad for pressingengagement therewith, a hollow, shell-like casing fixedly mounted onsaid flange, an inner shell having one surface thereof contoured todefine an acoustical chamber and a second surface thereof contoured todefine retaining means for sound receiving apparatus, and said innershell being yieldably mounted on said ear pad interiorly of said casingfor opposed relative movement to said casing in response to externalpressure upon said casing.

2. An acoustical coupling device comprising a pliable circumaural earpad having a fluid filling, a rigid flange mounted on said ear pad forpressing engagement therewith, an annular rigid shell-like casingfixedly mounted on said flange, a'rigid shell positioned interiorly ofsaid casing and having a first surface contoured to define acousticalapparatus retaining means and a second surface contoured to define anacoustical cavity terminating ing a peripheral rim, said rim of saidshell being mounted 'on said ear pad independently of said casing,resilient cushioning means mounted between said shell and said casingto' isolate said shell with respect to said casing,

whereby vibrative forces caused by sound waves impinging upon theexternal surface of said casing impart oscillatory motion to said casingand said vibrative forces are transmitted from said casing to said shellthrough said fluid filling of said ear pad causing oscillatory motion ofsaid shell out of phase with the motion of said casing to cancel theeffect of the vibrative forces upon said shell.

3. An acoustical coupling device comprising an annular fluid-filled ear.pad for contacting the head of the user, an annular rigid casingmounted on said ear pad for pressing engagement therewith, an annularrigid shell positioned interiorly of said casing and independentlymounted on said ear pad, said shell having a' first surface contoured todefine retaining means for sound receiving apparatus and a secondsurface contoured to define an acoustical chamber, resilient positioningmeans mounted between said casing and said shell whereby said shell isisolated from vibrating forces imparted to said casing from externalsources.

4. In an earcushion for an electrical headset, an annular circumauralear pad for contacting the head of the user, said ear pad comprising athin pliable material having a fluid filling, a hollow shell-likeannular casing, a rigid flange fixedly attached-to said casing andmounted on said ear pad for pressing engagement therewith, a shellinclosed within said casing having sound translating apparatus retainingmeans defined by one surface and an acoustical chamber defined byanother surface, said acoustical chamber having a volume defined by thelimiting surfaces of said chamber when said earcushion is placed againstthe head of the user, sound translating apparatus fixedly mounted insaid retaining means, and resilient positioning means to cushion saidsound translating means from vibrating forces imparted to said shell inresponse to vibrating forces applied externally of said casing, wherebysaid volume of said acoustical chamber remains substantially constant.

5. An acoustical coupling device comprising a rigid annular casing, arigid annular shell yieldably positioned within said casing and having afirst surface contoured to define retaining means for sound translatingapparatus and a second surface contoured to define an acoustical cavityhaving a volume defined when said coupling device is placed against thehead of the user, resilient positioning means mounted between saidcasing and said shell, and hydraulic means responsive to forces appliedto said casing to transmit said forces to said shell causing said shellto move relative to said casing, whereby said resilient positioningmeans oppose the relative movement of said shell and said casing toallow said volume of said acoustical cavity to remain substantiallyconstant.

6. An earcushion for an earphone headset comprising a circumaural earpad having a fluid filling for conforming to the contours of the head ofthe user, a rigid flange yieldably mounted on said ear pad, an annularhollow casing fixedly mounted on said flange, an acoustical shell havinga surface thereof contoured to contact the peripheral margins of the earand mounted on said ear pad independently of said casing and inclosedwithin said casing, and resilient means positioned between said shelland said casing, whereby vibrative forces caused by sound waves producedexternally of said casing tending to impart oscillatory motion to saidcasing and hence to said shell through said fluid-filling of said earpad are damped by said resilient means to cancel the oscillatory motionof said shell.

References Cited in the file of this patent UNITED STATES PATENTS2,235,372 Kalbitz Mar. 18, 1941 2,946,862 Wadsworth July 26, 1960FOREIGN PATENTS 126,746 Great Britain May'22; 1919

